Vending systems for hot food

A vending system for hot food comprises stacks (34) of food-containing trays of a standard size, a microwave oven (31) whose horizontal dimensions are similar to those of the trays and whose vertical dimension is preferably such as to produce a resonant cavity for the wavelength used, and means (44,45) for feeding a selected one of the trays (11) into the microwave oven on demand. The radiation is preferably introduced through a waveguide (321) into the top of the tray. Each tray preferably carries heating instructions (25) in machine readable code, e.g. as apertures on lateral extensions of a horizontal flange (12), and a reading head (52) reads the instructions and adjusts the microwave oven accordingly. The stacks (34) of trays may be held in a rotary magazine (33) and selected by push-buttons (35).